Security systems are used for detecting breakage of a glass pane of a window. Such systems typically include means for detecting breakage of the glass and means for responding to such breakage. Complex electronic shock sensors have been suggested for detecting vibrations corresponding to glass breakage, such as in U.S. Pat. No. 3,863,250 to McCluskey, Jr. For use in a motor vehicle, such systems involve undesirably high costs in producing the shock sensor and attaching it to each glass pane in the vehicle.
Other systems have employed conductive coatings or strips forming a closed loop around the outer perimeter of a glass pane, such as in U.S. Pat. No. 3,609,739 to Walter. Such full perimeter strips, however, present appearance problems for motor vehicle windows and, in addition, present an unacceptable risk of accidental disruption of the electrical continuity of the strip by scratching or the like due to the extent to which it is exposed to view and unintended contact.
It is an object of the present invention to provide a motor vehicle glazing unit security system which is economical to produce in the context of motor vehicle assembly, has good aesthetic qualities, and provides good durability over prolonged use. Further objects of the invention will be apparent from the following disclosure.